Silicon substrates in the form of silicon wafers used in the production of semiconductor substrates are subjected to various types of treatment such as photolithography, deposition treatment or polishing treatment, and are used to provide semiconductor devices. Silicon wafers are applied to numerous processing steps for the purpose of fabricating semiconductor devices, and since there is a need to improve the yield of semiconductor devices, there are strict requirements on the surface quality of the silicon wafers. Chemical mechanical polishing (CMP) has conventionally been used for mirror-polishing silicon wafers to ensure the surface quality thereof.
When polishing a silicon wafer using CMP, typically the silicon wafer is held in a carrier for immobilizing the wafer and clamped between upper and lower surface plates adhered with an abrasive cloth comprised of a synthetic resin foam or suede-like artificial leather, followed by polishing by pressing and rotating the silicon wafer while supplying an aqueous composition dispersed with colloidal particles such as silica, alumina, ceria or zirconia particles (to be referred to as a slurry composition).
In the case of CMP used on silicon wafers, there is a growing demand for improved productivity and surface quality accompanying the increased demand, higher performance levels and higher integration levels of semiconductor devices, and examples of areas where improvements can be made include improved removal rate, surface roughness, haze (surface clouding), flatness (roll-off (end face shear drop), SFQR, ESFQR) and scratch reduction.
Among these required properties, in order to improve decreases in the yield of semiconductor substrates caused by defects in the silicon wafer, it is effective to improve the haze (surface clouding) of the silicon wafer in the CMP process. Various technologies have previously been proposed for improving the surface status of silicon wafers after polishing. For example, Japanese Unexamined Patent Publication No. 2011-97045 (Patent Document 1) describes a technology for improving haze that also improves removal rate by adding an alkylene diamine composition containing a propylene oxide structure to a polishing composition used in CMP.
In addition, Japanese Unexamined Patent Publication No. 2011-97050 (Patent Document 2) describes the application of CMP after adding an alkylene diamine composition containing an oxyethylene group and oxypropylene group to a polishing composition in order to improve surface properties of a silicon wafer after final polishing. Moreover, Japanese Unexamined Patent Publication No. 2013-31914 describes a polishing liquid for electronic materials that is resistant to scratching and contains a fatty acid amine salt that reduces the number of particles adhered to the substrate after polishing.
Although these technologies are known, there has continued to be a need to provide a silicon wafer that realizes suitable removal rate and demonstrates improved surface clouding (haze) in order to improve the product yield of semiconductor substrates.